1. Field of the Invention
The present invention relates generally to fungicides/bactericides. More specifically, the present invention relates to a fungicide/bactericide composition which is based upon a complex of copper and a carboxylic acid derivative, and a method of making and using the fungicide/bactericide composition.
2. Background Art
Fungi are a large group of nongreen plants dependent upon the organic food made by photosynthesizing green plants. They represent a constant and ever present threat to many agricultural crops ranging from tropical and semi-tropical vegetation to temperate climate crops. Thus the control of phytopathogenic fungi is of great economic importance since fungal growth on plants or on parts of plants inhibits production of foliage, fruit or seed, and the overall quality of a cultivated crop. In addition, certain groups of fungi produce mycotoxins in infected crops, directly posing a health hazard to humans and animals. Fungicides are known in the art as either chemical or biological agents used to mitigate, inhibit or destroy fungi. To be economical, the cost of controlling plant diseases must be offset by increased crop yield and quality.
The use of Cu2+ ions for protecting crops against phytopathogenic fungi has been known for a long time. As early as 1882, a Bordeaux mixture was used to control the downy mildew on grapes. The Bordeaux mixture consisted of a light blue gelatinous precipitate suspended in water and formed by reacting 4 pounds of copper sulfate with 4 pounds of hydrated lime (calcium hydroxide) in 50 gallons of water. Later, various variations of the Bordeaux mixture have been made by changing the ratio of the components.
Presently, copper based fungicides/bactericides are used extensively in agriculture. It has been observed that various types of copper compounds can be used to effectively treat various plant pathogens, and are available in different types of formulations including wettable powders, emulsifiable concentrates, water-based flowables and dry flowables (also known as water dispersible granules). Dry flowable products are generally dustless, free-flowing, granular products. They are popular among users because the products can be formulated with a higher percentage of active ingredient, are easy to use and have improved shelf life compared to the aqueous fungicides/bactericides. Dry bactericides/fungicides can be stored for a long period of time, over wide extremes of temperature, without destroying the stability of the formulation. Dry bactericides/fungicides formulations also result in lower shipping cost.
While copper compounds have been known for their ability to control fungi/bacteria, the copper materials applied must be relatively non-toxic to the plants. Generally, inorganic copper compounds have been used because they have been observed to be non-phytotoxic, whilst most of the organic copper compounds have been found phytotoxic, especially in foliar applications.
With respect to the inorganic copper compounds, water soluble copper compounds are known to be extremely phytotoxic. As a result, water insoluble copper compounds are used as fungicides/bactericides. However, the low water solubility of the copper compounds presents a different kind of problem.
Biological activity of the copper-based fungicides/bactericides is measured by the free Cu2+ ions available for consumption by the fungi or bacteria. The biological activity of a fungicide/bactericide increases with an increase in the amount of free Cu2+ ions released. Therefore, the fungicides/bactericides formulated based on water insoluble copper compounds are normally applied in relatively large amounts to effectively control the phytopathogenic fungi. As a result, the relatively high level of copper detracts from cost effectiveness, contributes to soil residue contamination and raises the potential for phytotoxicity.
As an alternative to high level copper compound usage, the water insoluble copper compounds can be milled to fine particle size to increase the surface area of the compounds. The finer the copper compound, the more surface area it can cover with relatively small amounts of copper compounds. However, the methods employed to reduce the particle size of the copper compounds are not always cost effective. In addition, as a practical matter, it is difficult to disperse the finely milled copper compounds because of the tendency of fine particles to agglomerate.
Aside from process and formulation modifications, it is known that a copper complex or copper chelate can be used as a source of free Cu2+ instead of water insoluble copper compounds. It has been demonstrated that certain types of copper complexes or chelates are substantially nonphytotoxic and effective fungicides/bactericides for agriculture use.
U.S. Pat. No. 6,139,879 describes an aqueous bactericide/fungicide containing a complex of copper and ethylenediamine-di-o-hydroxyphenylacetic acid (EDDHA).
U.S. Pat. No. 6,471,976 describes an aqueous bactericide/fungicide containing a complex of copper and a partially neutralized polycarboxylic acid. While the bactericides/fungicides reduce the usage of copper compounds, the bioavailable copper from the complexes based on copper hydroxide ranges only from 217 ppm to 3530 ppm (see Table 1 and Table 2).
U.S. Pat. No. 6,562,757 describes a plant-protection composition comprising a copper source in non-chelated form and sparingly soluble calcium, zinc or manganese chelate. Upon application of the composition, copper chelates are formed in situ and gradually released to extend the application interval. U.S. Pat. No. 6,562,757 also describes a process of making the claimed composition by mixing and milling all the dry and powdery ingredients. While the gradual release of Cu2+ ions may be advantageous, it is desirable for a fungicide/bactericide to have an effective initial Cu2+ ion concentration to provide immediate antifungal/antibacterial effect. It is also desirable to have a process of making a fungicide/bactericide substantially dust-free.
Global health and environment regulations are becoming more and more stringent with respect to unmanaged or unnecessary fungicide/bactericide residues. Farmers around the world are facing a paradox. On one hand, the need to control destructive pathogens requires more fungicide/bactericide use. On the other hand, increasing pressures from regulatory agencies demand less chemical residue on crops and in the soil.
Therefore, a need exists for a copper-based fungicide/bactericide having high biological activity over typical copper-based products, while requiring significantly less copper in the formulation. A need exists for a copper-based fungicide/bactericide having immediate and extended antifungal/antibacterial effect. A need also exists for a process to make and use such fungicide/bactericide cost effectively and environmentally friendly. A way to meet these needs has now been found using the present invention.